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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c208552f4f31e7c2538cb4d2f75a9390abd4d07e260921d2f20ca61bbcd33bc9' 
  AND token = 'VfafUDGsDlSej7Vh7ZIFmyXnaI8DaAQQrVQvmMu8CME=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}